Secure copy will just copy the dx stub files (been there, done that, overnighted a USB hard drive). You may want to see if you can get a copy of emcopy from EMC as it may be stub-aware. You have to be careful of how DX was configured because if you've oversubscribed the disk (common in DX) and the method you use recalls all of the files you'll end up with a full disk and a lot of problems. Passthru reads with DX can be incredibly slow especially if you are using a Centera on the backend.
Are you trying to recall the files and copy them? The "fancy" tools just copy the stubs - xcopy will recall the data. Depending on your DX settings the data will be read passed-thru or will end back up on primary storage. Is your destination the filer or just another LUN on a new filer?
RepliStor is stub-aware if you need to go down that road. The good thing about Replistor is that your cutover time will be minimal as it'll keep the source and destination synchronized (and yes you can have a NAS voume as a destination with Replistor).